1. Field of the Invention
The present invention relates to reheat furnaces and, more particularly, to a drop-out conveyor for a pusher-type slab reheat furnace for discharging a product such as a slab from the furnace hearth line to an adjacent processing line external of the furnace such as a hot rolling mill.
2. Description of the Prior Art
In general, pusher-type slab reheat furnaces include a drop-out slope at a discharge end of the furnace in which the slope is used to gravity feed slabs from a furnace hearth line to an adjacent processing line external of the furnace. A conventional pusher-type reheat furnace arrangement is illustrated in U.S. Pat. No. 4,449,922 to Finke. The sliding of the slabs down the furnace discharge slope onto an external conveyor can damage the conveyor and, more significantly, can damage the slabs, possibly increasing the yield loss or incorporating defects into the work product.
Various attempts have been made to provide for mechanical unloading structures for heating furnaces. U.S. Pat. No. 4,421,481 to Holz et al. utilizes an unloading structure located adjacent a discharge end of a slab heating furnace for unloading the heated slab from a carriage traveling through the furnace. The unloading structure is a reciprocating, vertically movable forklift-type device. The Holz et al. design additionally incorporates a complex arrangement for returning the carriage to the beginning of the furnace to transport another slab therethrough.
U.S. Pat. No. 4,938,690 to Thomlinson et al. discloses an ingot heating furnace which utilizes an ingot-handling pivoted table at the exit of the furnace. The ingots are held upright on shoes as they are transported through the furnace.
U.S. Pat. No. 2,504,707 to Lloyd discloses a furnace for heating ingots in which the ingots travel through the heat furnace on carriages and then are subsequently removed from the carriages by a crane reciprocating between the exit of the furnace and the table for subsequent processing on a rolling mill.
U.S. Pat. No. 726,814 to Carroll discloses a billet heating furnace which utilizes a chain drive extending therethrough for driving a workpiece through the furnace. The chain drive continues from the exit of the furnace through a water cooling pit to the beginning of the furnace to complete the chain loop.
These prior art designs suffer from several distinct disadvantages. First, the systems do not represent cost-effective solutions for pusher-type slab reheat furnaces. Additionally, none of these designs can be easily retrofitted for incorporation into pusher-type slab reheat furnaces. The object of the present invention is to provide an economic solution for pusher-type slab reheat furnaces which can be incorporated into new facilities or easily retrofitted into existing pusher-type slab reheat furnaces.